Oxford Harlequins upset the formbook to comprehensively defeat South West 1 leaders and local rivals Chinnor 29-15.
Chinnor failed to match Quins' intensity and their first league loss of the season saw them slip to second in the table.
Quins underlined their potential with a display that gathered pace as the match went on, but must now repeat these levels if they are to be a genuine top-four side.
Forwards Phil Rowe, Chris Alcock and Dave Payne were all outstanding, as was full back Mark Preston, but Quins had the edge from one to 15.
This was a feisty clash from the start with Quins prop Paul DeLange landing some hefty punches on Chinnor rival Joe Winpenny in just the second minute.
But there was little skill on offer in the swirling wind.
The penalty count was high with referee Dino Maddern having to be extremely vigilant, but neither side opted to kick for goal.
Quins had most of the possession and territory with flanker Alcock being stopped just short on 13 minutes.
Rowe reacted well to stop a counter attack from Chinnor centre Trevor Powell, while the hosts saw prop Chris Aldous sin-binned for stamping after 20 minutes.
Chinnor raised their game after the half hour and Alcock had to be at his most alert to stop flanker Adam Hastings crashing through.
The visitors' power told when flanker Andrew McGuire was driven over on 34 minutes, but they never really kicked on from here.
Quins' centre Beau Wilson was denied a try after fly half Frank Jones gave him a forward pass.
Beau Wilson had a hand in an excellent stoppage-time score for Aldous after catching Preston's fine cross-kick and combining with fellow centre Andy Henley.
Jones's conversion made it 7-5 at the break and Quins simply raised their game.
A Jones penalty stretched their advantage and it was 15-5 after 52 minutes.
Chinnor full back Ben Hewitt failed to defend a high ball, allowing Payne to feed Rowe for try No 2.
The visitors were clearly rocked and brought on Ed Rixon to give them more bite in the loose.
DeLange was soon yellow-carded and you wondered if the hosts might falter.
However, Payne cantered through some weak defence on 61 minutes and was even able to celebrate before grounding the ball for Jones to convert.
Wing Jaike Carter found some rare space to finish well as Chinnor pegged the score back to 22-10.
But the game was well and truly over when replacement Andy Noyce showed great intelligence to find the supporting Henley for try No 4.
There was still time for Quins' replacement prop Nick Goodger to be sin-binned just three minutes after coming on and for Rixon to score a chargedown try.
Bracknell's defeat of Reading saw them return to the top on points difference and Chinnor must now wait two weeks to re-ignite their promotion challenge at home to St Ives.
Oxford Harlequins: Preston, Johnson (Noyce 59), A Henley, Wilson, Davies, Jones, A Cope (capt), Aldous (Goodger 75), Needham, DeLange (Goodger 77), Payne, Eckert, Rowe, Alcock (Gerber 49-52 blood & 59), Soper.
Chinnor: B Hewitt, Carter, Williams, Powell, O'Mahony, Cathcart, Gustafson, Winpenny, Stennings, Whelan, Hutchings (capt), Millburn, Hastings (Rixon 57), McGuire, Winslade.
Referee: D Maddern (Gloucester).
Man-of-the-match: Rowe.
Pictured are Quins' players clebrating Phil Rowe's try in their win against Chinnor.
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